One of the goals in the fabrication of electronic components is to minimize the size of various components. For example, it is desirable that hand held devices such as cellular telephones and personal digital assistants (PDAs) be as small as possible. To achieve this goal, the semiconductor circuits that are included within the devices should be as small as possible. One way of making these circuits smaller is to stack the chips that carry the circuits.
A number of ways of interconnecting the chips within the stack are known. For example, bond pads formed at the surface of each chip can be wire-bonded, either to a common substrate or to other chips in the stack. Another example is a so-called micro-bump 3D package, where each chip includes a number of micro-bumps that are routed to a circuit board, e.g., along an outer edge of the chip.
Yet another way of interconnecting chips within the stack is to use through-substrate vias. Through-substrate vias extend through the substrate and are thereby capable of electrically interconnecting circuits on various chips. Through-substrate via interconnections may provide advantages in terms of interconnect density compared to other technologies. In addition to applications in 3D chip stacking, through-substrate via interconnections may be used to increase performance of RF and power devices by providing very low resistive ground contacts to wafer backside and advanced heat sink capability. However, introduction of such interconnects may introduce additional challenges.
The integration of chips in 3D brings forth a number of new challenges that need to be addressed. Hence, what is needed in the art are improved structures and methods of making conductive interconnects such as through-substrate vias.